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Tripartite Motif Protein 32 Facilitates Cell Growth and Migration via Degradation of Abl-Interactor 2

Departments of ¹ Biochemistry and ² Otolaryngology, Head and Neck Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan

Requests for reprints: Shigetsugu Hatakeyama, Department of Biochemistry, Hokkaido University Graduate School of Medicine, N15, W7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan. Phone: 81-11-706-5899; Fax: 81-11-706-5169; E-mail: hatas{at}med.hokudai.ac.jp.

Key Words: TRIM32 • ubiquitin • Abl • Abi2 • proteasome

Tripartite motif protein 32 (TRIM32) mRNA has been reported to be highly expressed in human head and neck squamous cell carcinoma, but the involvement of TRIM32 in carcinogenesis has not been fully elucidated. In this study, we found by using yeast two-hybrid screening that TRIM32 binds to Abl-interactor 2 (Abi2), which is known as a tumor suppressor and a cell migration inhibitor, and we showed that TRIM32 mediates the ubiquitination of Abi2. Overexpression of TRIM32 promoted degradation of Abi2, resulting in enhancement of cell growth, transforming activity, and cell motility, whereas a dominant-negative mutant of TRIM32 lacking the RING domain inhibited the degradation of Abi2. In addition, we found that TRIM32 suppresses apoptosis induced by cis-diamminedichloroplatinum (II) in HEp2 cell lines. These findings suggest that TRIM32 is a novel oncogene that promotes tumor growth, metastasis, and resistance to anticancer drugs. [Cancer Res 2008;68(14):5572–80]